Page 1541 - College Physics For AP Courses

Chapter 34 | Frontiers of Physics 1529
strong gravitational field near the event horizon. One member of the pair falls into the hole and the other escapes, conserving momentum. (See Figure 34.17.) When a black hole loses energy and, hence, rest mass, its event horizon shrinks, creating an even greater gravitational field. This increases the rate of pair production so that the process grows exponentially until the black hole is nuclear in size. A final burst of particles and rays ensues. This is an extremely slow process for black holes about the
mass of the Sun (produced by supernovas) or larger ones (like those thought to be at galactic centers), taking on the order of years or longer! Smaller black holes would evaporate faster, but they are only speculated to exist as remnants of the Big
Bang. Searches for characteristic -ray bursts have produced events attributable to more mundane objects like neutron stars accreting matter.
Figure 34.14 This Hubble Space Telescope photograph shows the extremely energetic core of the NGC 4261 galaxy. With the superior resolution of the orbiting telescope, it has been possible to observe the rotation of an accretion disk around the energy-producing object as well as to map jets of material being ejected from the object. A supermassive black hole is consistent with these observations, but other possibilities are not quite eliminated. (credit: NASA and ESA)
Figure 34.15 The control room of the LIGO gravitational wave detector. Gravitational waves will cause extremely small vibrations in a mass in this detector, which will be detected by laser interferometer techniques. Such detection in coincidence with other detectors and with astronomical events, such as supernovas, would provide direct evidence of gravitational waves. (credit: Tobin Fricke)